After consideration, you have a point. With reviewing movies, the system naturally focuses on how ‘good’ the movie is. With this, I guess it focuses on how ‘useful’ I think it is? With my movie scale, anything above a 6 is a decent movie. 9+ is a really good movie. Perfect 10s happen rarely, but only on movies I truly love.

But with the RPG variation, the focus is much skewed. If utility is indeed the goal of these manuals, then they should be engineered by their authors as being as close to 10s as possible. That’s how it should work. Sadly, it doesn’t always.

So, without any data and baseline ratings, anything ‘good’ and up is probably a 9 and higher. (There’s not really a higher built into the numbers, but if you go and rate a bunch of things, you can quickly see that not all 10s are created equal, even though they are on the scale.) Something mediocre is, I dunno, 6-8? And anything 5 and below is really bad at what it does and probably isn’t worth buying.

Also, the scale is mostly from the DM perspective. I don’t know if a casual player needs to pay any attention to anything other than the first 2 bits.

And I’m going right now to do the rating for the other 5e books, cuz that was a good and useful point.